Semester 1 all lectures. Flashcards
What is the hydrological cycle?
This describes the movement of all forms of water on, in and above the earths surface.
Why is the hydrological cycle important?
It is an unlimited resource on a global scale, the largest circulation of matter in the earth-atmosphere system, primary biological production, major transporter of heat and key in the greenhouse effect.
Is the hydrological cycle open or closed? What does this mean?
It is an open system, changing in response to astronomical, geological and biotic factors.
What is the hydrosphere?
A series of reservoirs interconnected by water cycling in various phases, e.g. the ocean, the cryosphere, terrestrial water, water in the biosphere and the atmosphere.
What is the cryosphere?
Ice sheets, glaciers and seasonal snow/ice.
What is terrestrial water?
Rivers, soil moisture, lakes and ground water.
What is water in biota/in the biosphere?
Water in the plants/animals.
The volume of water is … but the supply of water is …
The volume of water in finite, but the supply of water is infintie.
Some water is broken down or created by volcanic eruption, is this a large amount?
No, its negligible.
By what volume has water increased over billions of years?
1 km3 a-1 dues to degassing of the earths mantle as water is chemically bound in rocks.
How is water cycling accomplished?
Evapouration, transport in the atmosphere, condensation, precipitaion and terrestrial runoff.
What is the largest store of water in the hydrosphere?
The oceans.
What are the two smallest stores in the hydrosphere?
Man-made reservoirs and irrigated soils.
There is more evapouration from the oceans than is precipitated back into the oceans, by how much?
40,000 km3.
What is the total volume of water in the hydrosphere?
Roughly 1500 billion km3.
What % of all water is in the oceans? How long does it stay there?
95-98% - 3.6 ka
What % of water is in the atmosphere? How long does it stay there?
0.001% - 10 days
80% of fresh water is where? How long does it stay there?
Ice. it stays here for 15 ka
How long does water stay in ground water stores?
10 ka
How long does water stay in rivers?
Day-weeks
How much faster do freshwater stores turnover than saline? (excluding ice) And why?
3-5 times faster. Terrestrial waters get more exposure.
What factors effect water turnover?
The amount of energy available, how efficient this energy is and the case of exchange.
How much moisture does evapouration put into the atmosphere from the oceans and from land.
Oceans - 87% - 150cm over tropical oceans a year.
Land - 13%
Water losses from plants are called?
Transpiration
Evapouration and transpiration are hard to seperate so what term is used?
Evapotranspiration.
Define precipitation.
The deposition of water from the atmosphere in liquid and solid form.
Moisture in the atmosphere ‘cascades’ what does this mean and what are the proportions?
25% condenses to rain, 75% forms ice and snow, then 70% melts to rain, the remaining 5% snow and ice crystals.
Humans are dependent on what stores?
The smallest, terrestrial stores. Only freshwater.
What are factors the effect the earths radiation balance?
Sun-earth relations (milankovitvh cycles),
the suns emissions,
the earth-atmosphere propertites (shape of the globe, greenhouse effect)
What are the 3 milankovitch cycles?
Eccentricity - 100,000 year cycle. Stretch.
Obliquity - 40,000 year cycle. Tilt,
Precession of the equinox - 20,000 year cycle. Wobble.
What can our eyes see on the electromagnetic spectrum?
The visible light. The peak of solar radiation.
What is the wavelength?
Distance from one peak or trough to the other.
What is the Stefan-Boltzmann law?
e = σT^4
Radiation emitted increases very much faster as temperature of emitter rises.
What is Wien’s law?
λ = 1/T or T-^1
Hotter objects emit shorter wavelengths of radiation,
E.g.
Red hot to white hot
The sun emits short or longwave radiation?
Short
The earth emits long or short wave radiation?
Long wave reflections of the suns radiation.
What are the two sunspot minimums and when were they?
The maunder minimum - 1659 to 1700.
Dalton minimum - 1800 ish
What was the sunspot maximum and when was it?
Modern maximum, 1950 ish
Are rainfall and sunspot numbers linked?
Yes, rainfall increases with sunspots.
Do all solar beams reach the earth?
No, gamma rays, x rays and ultra violet are stopped by the atmosphere.
What is the albedo of water bodies?
10-60%
What is the albedo of the moon?
6-8%
What is the albedo of fresh snow?
80-95%
What is the albedo of forests?
10-20%
What is the albedo of crops/grassland?
10-25%
What is the albedo of grass?
25-30%
What is the albedo of asphalt (blacktop)?
5-10%
What is the albedo of concrete?
17-27%
What is the earths average albedo?
31%
What is the albedo of brick/stone?
20-40%
What is the albedo of a light roof?
35-50%
What is the albedo of a dark roof?
8-18%
Clouds tend to trap and reflect what radiation
Trap longwave and reflect shortwave
Difference between high and low clouds at reflection and trapping radiation is?
High clouds reflect less solar radiation but still trap the earths radiation.
Low clouds are better at reflection radiation.
Conduction definition
Transfer of thermal energy between neighbouring molecules due to temperature gradient to equalize temperature.
Convection definition
Fluid motion in which warm air rises or cold air sinks.
Advection definition
The transfer of a property of the atmosphere such as heat, cold or humidity by horizontal movement of air mass.
Radiation definition
The transfer of energy between two bodies without the aid of an intervening medium at the speed of light.
Latent heat definition
The thermal energy involved in a change of state i.e. energy used when water changes from a liquid to vapour during evapouration and released when water vapour condenses to liquid.
Balance equation for surface heat budget simplified to what?
Qnet + Qs + Ql = Qresidual
What is net radiation?
The resultant flux of solar and terrestrial radiation through a horizontal surface - the balance of radiation between input and output.
Do the poles have a postitive or negative net radiation?
Negative.
Does the equator have a positive or negative net radiation?
> 80 net radiation.
What is the difference between direct and oblique radiation?
Direct radiation arrives parallel to the earths sureface and is more concentrated, oblique is more diffuse.
The equator recieves what surplus of incoming energy? What does this cause?
Surplus 30 degrees north to 30 degrees south.
This fuels the circulation of the atmosphere.
Does land/sea make a difference to radiation absorbed?
Yes, different albedos.
Net radiation decreases more than solar radiation does as you move towards the poles, why is this?
There is an increased albedo as you move towards the poles and oceanic absorption is higher in the tropics.
What is the speed of land and oceans cooling?
Land warms and cools much faster the bodies of water. There is no mixing in land, water is transparent so deeper warming can occur.
What has a higher range in temperatures generally, land or sea?
Land, especially in northern latitudes.
What is sensible heat?
Heat transfer by convection or conduction where heat is transferred by the rising and mixing of warm air.
Sensible heat increases pole wards at sea but decreases pole wards on land, why is this?
This is because water warms air more than land because of its heat capacity in higher latitudes.
Ocean circulation brings warm water to higher latitudes so there is more sensible heat to be released.
There is more latent heat over the oceans, why is this?
There is no limits to evaporation and the sea absorbs more radiation.
When does evaporation occur? What happens?
When energy is transported to an evaporating surface where the air pressure above is below saturation value. It requires energy to overcome the inter molecular attraction. Energy is acquired by heat from immediate surroundings, latent heat lost and temperatures drop.
Wind speed above creates air turnover for evaporation to occur.
Molecular evaporation definition is?
The addition of kinetic energy makes the molecules velocity increase, more likely for an individual molecule to escape the surface of the water. Fastest escape first.
What is the formula for evaporation rate?
Evaporation rate = f(u) (e,saturated–e,actual).
U = wind speed and (e,saturated–e,actual) = the saturation deficit. Saturated being the max.
What is Dalton’s law.
e = vapour pressure – standard measure of water vapour content
Warmer air can hold more water vapour, what is this relationship called?
The Clausius-clapeyron relationship.
What is a Lysimeter?
This measures evapotranspiration by the change in soil weight.
Where globally is the most evaporation?
Mostly from the oceans, subtropical oceans away from the equator, or in the equator when there is cloud cover. Most evaporation on land occurs from tropical rain forests.
What are the three parts of the oceans vertical structure?
Ocean surface (thermally mixed 10m-400m) Thermocline (lower temp, higher density, stratified with little mixing 200m-1000m) Deep layer of cold, dense water, movement driven by density variations due to change in salinity.
How is the ocean effected vertically?
Effected by atmospheric circulations.
Example of a warm water current and how it effects evaporation.
The gulf stream/north Atlantic drift, increase in evaporation so more rain in Europe.
Example of a cold surface current and how it effects evaporation.
The west coast of south america and south Africa, reduced evaporation and the cause of deserts.
Why do surface currents head pole wards on the western side of oceans?
Due to the coriolis effect/the spin of the earth.
Hurricane belts are fueled by what over warm waters?
High evaporation.
What occurs with sea breezes at night?
Cool air is drawn inland as the land is warmed quicker (the air inland is rising)
What occurs with sea breezes during the day?
As the land is cooling faster the cool air is drown out to sea and the air above the sea is warmer so rising.
Differences in the thermal properties of land and sea are responsible for what events?
Monsoons.
What is El Nino?
A short term fluctuation, 2-7 years, a reversal in the winds in the equatorial Pacific. Opposed to the normal conditions where winds blow from south America to Indonesia. High pressure over Indonesia reverses this wind.
Impacts of El Nino are?
Flooding in Peru and Ecuador,
reduced cool water from deep down so fishing and birds suffer and south america.
North America warms.
Define rain
Falling water drops with a diameter of >0.5mm and typically 2mm.
Define snow
Ice crystals falling in branched clusters of snowflakes.
Define hail
Hard pellets, balls or irregular lumps of ice, at least 5 mm across.
Define graupel
Snow pellets of opaque conical or rounded ice particles, 2-5mm in diameter formed by aggregation.
Define sleet
Rain-snow mixture (uk)
Small, translucent ice pellets (us).
Define dew
Condensation droplets on the ground surface or grass, deposited when surface temperature is below the airs dewpoint temperature.
Define rime
Clear crystalline/granular ice deposited when supercooled fog encounter vertical structures.
What are causes of precipitation?
Convergence of air (uplift) orography/relief (adiabatic cooling) and ocean circulation.
What is adiabatic cooling?
When air rises, it expands as there is less air above, this cools without more or less heat added.
What is the dry adiabatic lapse rate?
That rising air cools and sinking air warms, 0.98 degrees per 100m rise.
What is the saturated adiabatic lapse rate?
This is when dew point has been reached in the air, heat is being released during condensation so the rate is 0.5 to 0.9 degrees per 100m rise.
Latent heat does what to the cooling and heating process in air?
Complicates it.
What are lifting mechanisms that create clouds?
Low pressure, plowed fields, orographic, and frontal.
What is a typical warm front?
The cold air mass is passive, the warm air gentle rises and creates clouds and drizzly rain as the warm front moves towards the cold.
What is a typical cold front?
Dense cold front forces warm air up abruptly, large clounds, raindrops and heavy showers/thunder and lightning occur.
What is a cumulonimbus thunder head?
A large cloud with circulation within it, tall and creates thunder and lightning.
How do droplets grow big enough to fall?
In clean air supersaturation is needed for condensation to occur, normal air is dirty and the dirt acts as condensation nuclei. This can be dust or sea spray directly or coagulation of small particles etc.
What are the three types of condensation aerosol?
Nonwettable and insoluble nuclei (useless).
Wettable but insoluble.
Hygroscopic nuclei - most efficient, they absorb water vapour below 100% humidity.
What are the different sizes of nuclei?
Giant nuclei 1-10 micro meters - useless unless hydroscopic.
Large nuclei 0.1-1 micro meter. more effective.
Aitken Nuclei 0.01-0.1 micro meter. Most effective. Any less is useless,
What is Coalesence and what is its relationship with condensation?
Happens after condensation, increases as condensation becomes less effective.
What is the Bergeron process?
Water prefers to stick to ice, so the water pressure around this is lowered, causing water off other droplets to evaporate of that due to the lower pressure and on to the ice crystal too.
Are all snow crystals the same?
No, they form differently at different temperatures and therefore different altitudes.
What are global precipitation patterns?
Equatorial maximum (slightly to north), west coast maxima, dry areas of subtropical high pressure cells (create major desserts) Low over high latitudes.
What is atmospheric pressure?
The pressing of the air in the atmosphere down on the earths surface. The molecules in the air are impacted by gravity.
Atmospheric pressure decreases with altitude, rapidly at first then more gradual.
What are Pascals (Pa)
Pressure as a force per unit area.
How do bars, millibars, pascals and mmHg compare?
1 bar = 1000mb = 10,000 Pa = 75 mmHg.
What is the Pa at 15 degrees at sea level?
101,320.
What does a Barometer measure?
Atmospheric pressure.
What is the key principle of pressure gradient?
Air, acting under gravity will always move to result in equal pressure.
What do isobars represent?
Areas of similar atmospheric pressure.
Wind definition.
The motion of air flow around the earths surface between areas of differing pressure, the greater the gradient, the stronger the win. Predominantly horizontal, vertical called updrafts or down drafts.
What are wind speeds measured by, and on what scale?
Anemometer on the Beaufort scale.
Who first describe the coriolis effect and when?
Gustave-Gaspard Coriolis 1835,
What is the coriolis effect?
Results from the rotation of the earth, deflects the path of an object e.g. parcel of air.
Northern hemisphere - deflects to the right.
Southern hemisphere -
deflects to the left.
What is deflected by the coriolis effect more, strong winds or weak winds?
Strong winds are deflected more.
What is the coriolis effect at the equator?
Zero.
Where is the coriolis effect strongest?
The poles.
What are frictional forces on wind?
The earths surface causes the wind to slow down and move in irregular ways.
How is global circulation divided?
The lower atmosphere and the upper atmosphere.
What is the jet stream?
Fast traveling wind where the pressure gradient is strong, stronger in the winter than the summer.
What are the two jet streams?
Polar which can go as far south as 35 degrees (Texas) and the subtropical jet stream which is between 20-50 degrees. There is also two in the other hemisphere. Move to the west and found in the tropopause.
What is the rossby wave?
The westward flow of the upper-air frequently forms undulations (flows in a “circle” to the west and has waves)
Sometimes smooth but warm air can move upwards causing the ripples and the cold air will poke out and eventually be cut off leaving a pocket of cold air further south than usual.
How do rossby wave influence the ocean?
Displace the thermocline and influence currents.
Who is the Hadley cell named after and when was it first discussed?
George Hadley in 1735.
What are Hadley cells?
A convection loop caused by heating at the equator due to the suns strength here. One per hemisphere, deflected eastwards due to coriolis.
What are the NE and SE trade winds?
Hadley cell air cools at 30 degrees, this air coming back to the equator is the trade winds.
What are the 3 cells that make up global circulation?
Hadley, ferrel and polar cells.
What is the polar cell?
Vertically smallest, one in each hemisphere, cold dense air slows flows from high pressure out south to roughly 60 degrees.
What is the ferrel cell?
Driven by the other two cells, surface winds move from south to north, and cause westerly winds. Between 60 and 30 degrees.
What are horse latitudes?
Areas of general subsidence in the zone between 20 and 35 degrees.
The flow from horse latitude to the equator is called what?
Trade winds. (there are others)
When trade winds from both hemispheres converge what is this light wind called?
Doldrums.
The three cells in the atmosphere mix the air how?
The Hadley cell is the tropical convection loop, the ferrel cell mixes cold and warm air, and the polar cell is the circulatory loop for polar regions.
What does ITCZ stand for?
Inter Tropical Convergence Zone.
What is the ITCZ?
Air that flows into the low pressure left by the hadly cell converges (joining of two trade winds) and brings heavy precipitation. Same as Doldrums.
At 30 degrees where the hadley cell descends there is high pressure, what is this area called?
The sub-tropical high pressure belts. They have clear skies and low precipitation. Deserts found in these areas,
The Hadley cells strength changes seasonally, what does this cause? And why does it change?
The ITCZ to move, and monsoons occur. It changes due to the suns position.
Does the ITCZ move more on land or on sea?
On land.